1. Field of Invention
The present invention relates generally to coaxial cable connectors, particularly F-connectors, that are designed to establish fail-safe grounding. More particularly, the present invention relates to coaxial F-connectors that establish enhanced grounding during installation through direct, internally crimpled contact with the coaxial cable sheath. Known prior art can be found within numerous subclasses of United States Patent Class 439, including subclasses 241, 247, 322, 548, 553, 554, 578, 583, 585, 587 and others.
2. Discussion of the Related Art
Popular cable television systems and satellite television receiving systems depend upon coaxial cable for distributing signals. As is known in the satellite TV arts, coaxial cable in such installations is terminated by F-connectors that threadably establish the necessary signal wiring connections. The F-connector forms a “male” connection portion that fits to a variety of receptacles, forming the “female” portion of the connection.
Typical F-connectors include a tubular post designed to slide over coaxial cable dielectric material and under the outer, conductive sheath at the prepared end of the coaxial cable. The exposed, conductive sheath is usually folded back over the cable jacket. The cable jacket and folded-back outer conductor extend generally around the outside of the tubular post and are typically coaxially received within the tubular connector. A continuity contact between the sheath and electrically conductive portions of the connector is needed. Moreover, electrical contact must be made with the F-connector threaded nut that contacts the female socket to which the connection is made. Stated another way, a fundamental goal with modern F-connectors is to establish a fail safe continuity path between the coaxial cable outer sheath, that makes contact within the F-connector, and the target socket to which the connector is threadably coupled, that makes contact with the connector exterior.
F-connectors have numerous advantages over other known fittings, such as RCA, BNC, and PL-259 connectors, in that no soldering is needed for installation, and costs are reduced as parts are minimized. For example, with an F-connector, the center conductor of a properly prepared coaxial cable fitted to it forms the “male” portion of the receptacle connection, and no separate part is needed. A wide variety of F-connectors are known in the art, including the popular compression type connector that aids in rapid assembly and installation. Hundreds of such connectors are seen in U.S. Patent Class 439, particularly Subclass 548.
However, the extremely high bandwidths and frequencies distributed in conjunction with modern satellite installations necessitates a variety of strict quality control factors. For example, the electrical connection established by the F-connector must not add electrical resistance to the circuit. The F-connector must exhibit a proper surge impedance to maintain a wide bandwidth, in the order of several Gigahertzes. Numerous physical design requirements exist as well. For example, connectors must establish and maintain a proper moisture seal against the environment, and they must function over long time periods through extreme weather and temperature conditions. Requirements exist governing frictional insertion and disconnection or withdrawal forces as well.
The establishment of proper electrical continuity is a paramount requirement. Low resistance electrical continuity throughout the connector contributes to proper grounding and shielding in use. Within the connector, it is important to establish effective electrical continuity between the F-connector nut and the internal, coaxial cable sheath. One facet of the problem involves the establishment of electrical continuity between the F-connector nut and the internal post. With most known F-connector designs, the coaxial cable sheath electrically contacts the shank of the internal post within the connector. Thus it is important that the F-nut and the internal post within the connector establish electrical contact with one another. With proper electrical contact between the nut and the post established, a dependable electrical connection between the F-connector nut and the coaxial cable sheath results via a multi-step process. Thus proper grounding is established with the target socket to which the connector is ultimately fitted.
Proper installation techniques require adequate torquing of the connector's F-nut. In other words, it is desired that the installer appropriately tighten the F-nut during installation to establish a dependable electrical grounding path between the connector body, the coaxial cable sheath, and the target socket. Threaded F-connector nuts should be installed with a wrench to establish reasonable torque settings. Proper tightening of the F-nut to the threaded female socket applies pressure to the inner conductor of the coaxial cable to establish proper connections within the socket. Further, proper torquing insures mechanical and electrical contact between the F-nut and the internal post. With many F-connector designs, proper tightening insures that portions of the tubular post directly engage outer conductive portions of the appliance port, thereby making a direct electrical ground connection between the outer conductor of the appliance port and the tubular post. Of course the tubular post is electrically in contact with the outer conductor or sheath of the coaxial cable, so a ground connection is established between the cable and the target port or socket.
Many connector installations, however, are not properly completed. It is a simple fact in the satellite and cable television industries that many F-connectors are not appropriately tightened by the installer. The common installation technique is to torque the F-connector with a small wrench during installation. In some cases installers only partially tighten the F-connector. Some installations are only hand-tightened. Furthermore, many installations are subject to repetitive disconnection and reconnection by the end user or customer. For example, in geographic locations subject to frequent high intensity lightning storms, it is prudent to disconnect internal household connections to major appliances during storms to prevent damage or even destruction from lightning. Afterwards, the connections are reestablished, usually only by hand tightening, and problems related to insufficient grounding appear.
As a consequence of insufficient connector tightening, degraded electrical continuity can occur. When F-connectors are not properly “grounded,” the electrical continuity is compromised. An appropriate low resistance, low loss connection to the female target socket, and the equipment connected to it, will not be established. Unless a proper ground path is established, poor signal quality, and RFI leakage, will result. This translates to signal loss or degradation to the customer.
U.S. Pat. No. 3,678,445 issued Jul. 18, 1972 discloses a shield for eliminating electromagnetic interference in an electrical connector. A conductive shielding member having a spring portion snaps into a groove for removably securing the shield. A second spring portion is yieldable to provide electrical contact between the first shell member and a second movable shell member.
U.S. Pat. No. 3,835,443 issued Sep. 10, 1974 also discloses an electromagnetic interference shield for a connector. A helically coiled conductive spring is interposed between mating halves of the connector. The coiled spring has convolutions slanted at an oblique angle to the center axis of the connector. Mating of the connector members axially flattens the spring to form an almost continuous metal shield between the connector members.
U.S. Pat. No. 3,739,076 issued Jun. 12, 1973 discloses a coaxial connector with an internal, electrically conductive coil spring mounted between adjacent portions of the connector. As an end member is rotatably threaded toward the housing, an inwardly directed, annular bevel engages the spring and moves it towards an electrically shielded portion of the cable. The spring is compressed circumferentially, so that its inner periphery makes electrical grounding contact with the shielded portion of the cable.
U.S. Pat. No. 4,106,839 issued Aug. 15, 1978 shows a coaxial connector with a resilient, annular insert between abutting connector pieces for grounding adjacent parts. A band having a cylindrical surface is seated against an internal surface. Folded, resilient fingers connected with the band are biased into contact. The shield has a plurality of folded integral, resilient fingers for establishing a ground.
U.S. Pat. No. 4,423,919 issued Jan. 3, 1984 discloses a connector with having a cylindrical shell with a radial flange, a longitudinal key, and a shielding ring fitted over the shell adjacent the flange. The shielding ring comprises a detent having end faces configured to abut connector portions when the detent fits within the keyway, whereby the shell is prevented from rotating.
U.S. Pat. No. 4,330,166 issued May 18, 1982 discloses an electrical connector substantially shielded against EMP and EMI energy with an internal, conductive spring washer seated in the plug portion of the connector. A wave washer made from beryllium copper alloy is preferred.
U.S. Pat. No. 5,066,248 issued Nov. 19, 1991 discloses a coaxial cable connector comprising a housing sleeve, a connector body, a locking ring, and a center post. A stepped annular collar on the connector body ensures metal-to-metal contact and grounding.
U.S. Pat. No. 6,332,815 issued Dec. 25, 2001 and U.S. Pat. No. 6,406,330 issued Jun. 18, 2002 utilize clip rings made of resilient, conductive material such as beryllium copper for grounding. The clip ring forms a ground between a male member and a female member of the connector.
U.S. Pat. No. 6,406,330 issued Jun. 18, 2002 employs an internal, beryllium copper clip ring for grounding. The clip ring forms a ground circuit between a male member and a female member of the electrical connector. The clip ring includes an annular body having an inner wall and an outer wall comprising a plurality of circumferentially spaced slots.
U.S. Pat. No. 6,716,062 issued Apr. 6, 2004 discloses a coaxial cable F connector with an internal coiled spring that establishes continuity. The spring biases the nut towards a rest position wherein not more than three revolutions of the nut are necessary to bring the post of the connector into contact.
U.S. Pat. No. 7,114,990 issued Oct. 3, 2006 discloses a coaxial cable connector with an internal grounding clip establishing a grounding path between an internal tubular post and the connector. The grounding clip comprises a C-shaped metal clip with an arcuate curvature that is non-circular. U.S. Pat. No. 7,479,035 issued Jan. 20, 2009 shows a similar F-connector grounding arrangement.
U.S. Pat. No. 7,524,216 issued Nov. 2, 2010 discloses a coaxial connector comprising a body, a post including a flange having a tapered surface, a nut having an internal lip with a tapered surface, wherein the tapered surface of the nut oppositely corresponds to the tapered surface of the post when it is assembled. A conductive O-ring between the post and the nut establishes continuity.
U.S. Pat. No. 7,845,976 issued Dec. 7, 2010 and U.S. Pat. No. 7,892,005 issued Feb. 22, 2011 use conductive, internal O-rings for both grounding and sealing.
U.S. Pat. No. 7,753,705 issued Jul. 13, 2010 discloses an RF seal for coaxial connectors. The seal comprises a flexible brim, a transition band, and a tubular insert with an insert chamber defined within the seal. In a first embodiment the flexible brim is angled away from the insert chamber, and in a second embodiment the flexible brim is angled inward toward the insert chamber. A flange end of the seal makes a compliant contact between the port and connector faces when the nut of a connector is partially tightened, and becomes sandwiched firmly between the ground surfaces when the nut is properly tightened.
U.S. Pat. No. 7,824,216 issued Nov. 2, 2010 discloses a coaxial connector comprising a body, a post including a flange having a tapered surface, a nut having an internal lip with a tapered surface which oppositely corresponds to the tapered surface of the post when assembled, and a conductive O-ring between the post and the nut for grounding or continuity.
U.S. Pat. No. 7,841,896 issued Nov. 30, 2010, and entitled “Sealed compression type coaxial cable F-connectors”, discloses axially compressible, high bandwidth F-connectors for interconnection with coaxial cable. An internal, dual segment sealing grommet activated by compression provides a seal. Each connector nut interacts with a tubular body and a rigid, conductive post coaxially extending through the connector. A post barbed end penetrates the cable within the connector. A metallic end cap is slidably fitted to the body. A tactile system comprising external convex projections on the body complemented by a resilient, external O-ring on the end cap aids installers who can properly position connectors with the sense of touch.
Similar U.S. Pat. No. 7,845,976 issued Dec. 7, 2010 and U.S. Pat. No. 7,892,005 issued Feb. 22, 2011 use conductive, internal O-rings for both grounding and sealing.
U.S. Pat. No. 7,892,024 issued Feb. 22, 2011 shows another grounding insert for enhancing F-connector continuity.
Structural improvements to compressible F-connectors for enhancing continuity or grounding must function reliably without degrading other important connector requirements. For example, compressible connectors must adequately compress during installation without excessive force, and without bending or deforming. An environmental seal must be established to keep out water or other contaminants. The coaxial cable inserted into the connector must not be mechanically broken or short circuited. Field installers and technicians must be satisfied with the ease of installation. Finally, the bottom line is that a long lived, reliable installation must result for customer satisfaction.
Electrical continuity in connectors has previously been accomplished by manufacturing all or a majority of the components of connectors from conductive materials such as copper or copper plated metals. Metal components are typically more expensive to manufacture and transport than non-conductive alternatives such as plastic components. However, it is the non-conductive property of plastics that has limited it use in prior-art connectors.
As implied from the above-discussed art, many prior art attempts at enhanced grounding exist. Several solutions involve the addition of auxiliary conductive grounding structures within the fitting. These can physically bear against critical parts or extend between them to enhance continuity. For example, several prior design approaches include structure that forcibly urges the internal connector post into pressured contact with the F-nut. Some designs include auxiliary internal structures that provide additional electrical connection paths between the F-nut and the post, and some such structures may include portions that contact the socket to which the fitting is attached. In most of these designs the coaxial cable sheath is connected to the structure by physical contact with the post, which in turn touches the F-nut. However, recent experience suggests that better continuity can be established by additionally urging portions of the conductive cable sheath into direct mechanical and electrical contact with portions of the F-nut. In other words, it is desirable to enhance electrical continuity by directly contacting the F-nut with the cable sheath, minimizing the connector components involved in the electrical connection path.